One method that can be used to achieve control of a polymer's molecular weight (MW) and polydispersity is through ring opening metathesis polymerization (ROMP). ROMP is valuable where undesirable termination and chain transfer reactions are either absent or insignificant and polymerization rates are usually very rapid with high MW polymers approaching 100 kDa often obtained within minutes.
Additionally, copolymers, such as di-block and tri-block co-polymers and gradient co-polymers, can be easily made by sequential addition of another monomer(s) after consumption of the previous monomer. Ruthenium (Ru)-based catalysts allow the polymerization of strained unsaturated cyclic monomers with numerous functionalities. Some of the most commonly polymerized monomers are norbornene and its derivatives. Polymerization over a wide range of functional groups may be easily-controlled. A concurrent, related interest for aqueous polymer systems is the use of poly(ethylene oxide) (or “PEO”) containing monomers. Such polymers may be used in various applications such as biomedical, water treatment, wound healing and other end-use applications where water-soluble polymers and/or hydrogels are useful.
Despite the wide spread use of some PEO functionalized polymers, little is known on PEO-functionalized norbornenes. No PEO water-soluble norbornene or other ROMP monomers are believed to have been prepared. Anionic polymerization of ethylene oxide from norbornene monomers containing a primary alcohol functional group was reported. This PEO-functionalized macromonomer was then polymerized using a Schrock-type catalyst to obtain polymers with high MWs (47-117 kDa) and polydispersity index (PDI) around 1.1 (for only one polymer). More recently, another approach involved the attachment of short EO units (n=4) to norbornene monomers. These monomers were further functionalized by reacting the hydroxyl end group of the EO with 2-bromopropionyl bromide to incorporate atom transfer radical polymerization (ATRP) initiators in the side chains. See, e.g., 15 Héroguez, et al. Macromolecules 1997, 30, 4791; Chemtob, et al. Macromolecules 2002, 35, 9262; Chemtob, et al. Macromolecules 2004, 42, 2705; Quémener, et al. Macromolecules 2006, 39, 5589; Héroguez, et al. Macromolecules, 1996, 29, 4459.